U.S. Pat. No. 5,219,277 discloses an electric motor gear rotor type fuel pump having intermeshing inner and outer gear rotors positioned within a housing of the fuel pump in cooperation with inlet and outlet ports of the housing for pumping fuel from a vehicle tank and delivering the fuel under pressure to a vehicle engine. The inner and outer gear rotors have a plurality of teeth which intermesh when driven by the electric motor of the fuel pump and define circumferentially disposed enlarging and ensmalling pumping chambers through which the liquid fuel is drawn and discharged under pressure. The teeth of each gear rotor have uniform and continuous faces forming smooth driving surfaces when intermeshed.
The design of these gears is limited by many physical factors including the number of teeth, amount of eccentricity between inner and outer gears, displacement, location of the fuel ports for the gears, and the necessary size of the teeth to withstand the forces applied to them in use. While these parameters may be independently varied, the overall shape of the tooth is generally constant and greatly limits the ability to optimize the gears as to drive angles and other parameters which effect the performance and durability of the gears.